The links where working yesterday, as I tested them. Now showing error 500. Kwikfit messing about again. My apologies.
None required.
My first thought was Motability / Kwik Fit have closed down open access to the ‘Fleet’ website to stop people checking if a neighbour or friend is in receipt of DLA / PIP.
When the tax disc was removed and replaced by entering the registration of a car via the .Gov website, it would show its class (PLG or Disabled). You may remember that was challenged by various disability organisations as a privacy issue (despite it being on the tax disc it replaced).
It just seemed unusual that one day it was operational, and the next gone. Although as you note, it could be an IT issue with Kwik Fit.